1. Field of the Invention
The present invention relates generally to a system and method for subsea separation of well fluids and solids and, more particularly, to a compact separating system that may be deployed and operated at deep and ultra-deep water depths for processing well fluids and solids prior to transport to the surface, or disposal either subsea or to the surface.
2. Description of the Background
In recent years, the oil and gas industry has found significant oil and gas reserves in deepwater offshore locations. Many discoveries have been made in over three thousand feet of water with a number of high potential discoveries being located in over five thousand feet of water. In the not too distant future, discoveries in depths of over ten thousand feet are inevitable. As the production depths increase, the cost of transporting well fluids from the seabed to the surface also increases. Transporting well fluids that contain significant amounts of undesirable solids and water from significant depths limits the flow of the desirable hydrocarbon products to the surface due to significant cost limitations of the internal diameter of the riser pipe from the sea bottom. Not only are there significant inefficiencies associated with transporting multi-phase fluid flow from the seabed but also there are other high costs including production problems such as erosion, corrosion, and hydrate formation. At the present time, technical and economical limitations effectively prevent profitable deepwater production. As the depths reach new levels, there is no current technology that can be used to commercially exploit deep water reserves. On the other hand, the medium to longer term strategic business plans of some oil and gas producers are dependent on the finding of appropriate technology to exploit deep water reserves.
The methods currently available to produce and separate the constituent hydrocarbon products from associated solids and produced water utilize production separation equipment that is located topside on fixed or floating facilities. It would be highly desirable if there were means to reduce the cost of these facilities and avoid the other aforementioned costs with a commercially feasible method of separating by-products of oil and gas production at the seabed. Unfortunately, the methods and systems for separating multiphase fluids presently used are not feasible in the remote, hostile, and problematic environment at the seabed in deep waters. Nonetheless, such a highly desirable means would preferably separate some unprofitable by-products, namely water and solids, on the seabed and dispose of them into the reservoir and/or onto the seabed.
Numerous speculative subsea separation solutions have been put forward where either one or two such separation processes occur. However, these processes are based on the use of conventional equipment that operates in a manner consistent with topside operations. These solutions fail to address all the issues associated with subsea separation because the adoption of conventional technology is impractical to use as a seabed system. For instance, in one proposed subsea separation method put forward, it is submitted the reliability is highly suspect due to unsolved problems that might be encountered such as erosion, corrosion, hydrate formation, and that furthermore the efficiency of the system is too low such that it would have flow through rates that are unprofitably low. In another proposed subsea system, the size of the system to be placed underwater is so large as to make the system economically unfeasible for use at significant depths. Topside systems cannot simply be lowered onto the seabed because of numerous problems that are encountered thereby.
It is submitted that the above discussed proposals for subsea operation do not provide a compact subsea production system that is commercially feasible for producing from significant depths. Consequently, there remains a need for an improved and compact deepwater production separation system that is capable of efficiently separating the constituents of hydrocarbons production, namely oil, gas, water, and solids. It would be desirable to have a system designed to operable in virtually any water depth and having significantly reduced size with respect to production efficiency as compared to existing technology. Thus, such a system would lend itself to be of particular value to production in much greater depths, such as water depths over ten thousand feet deep or more. Those skilled in the art have long sought and will appreciate the present invention which provides solutions to these and other problems.